Acetogenic microorganisms can produce ethanol from carbon monoxide (CO) through fermentation of gaseous substrates. Fermentations using anaerobic microorganisms from the genus Clostridium produce ethanol and other useful products. For example, U.S. Pat. No. 5,173,429 describes Clostridium ljungdahlii ATCC No. 49587, an anaerobic microorganism that produces ethanol and acetate from synthesis gas. U.S. Pat. No. 5,807,722 describes a method and apparatus for converting waste gases into organic acids and alcohols using Clostridium ljungdahlii ATCC No. 55380. U.S. Pat. No. 6,136,577 describes a method and apparatus for converting waste gases into ethanol using Clostridium ljungdahlii ATCC No. 55988 and 55989.
Many acetogenic microorganisms are poorly suited for industrial scale bioprocessing and have therefore not demonstrated commercial viability for this purpose. Such microorganisms have slow doubling time and low total productivities. In addition, many techniques for genetic manipulation (knockout, over-expression of transgenes via integration or episomic plasmid propagation) are inefficient, time-consuming, laborious, or non-existent.
Acetogenic microorganisms may be grown to produce ethanol from carbon monoxide. The growth process may involve culturing the acetogenic bacteria on increasing amounts of CO over time. There exists a need to more quickly develop microorganisms and methods of their use to utilize syngas or other gaseous carbon sources for the production of desired chemicals and fuels.